A largest artery that originates from a left ventricle of a heart, goes upward to form an aortic arch, and goes downward to end at a bifurcation of a common iliac artery is called an aorta. The aorta also serves as an originating source in blood circulation to an entire body. Similarly to other arteries, the aorta has a three-layer structure of an intima, a media, and an adventitia.
A condition called aortic dissection is one of the medical conditions pertaining to the aorta. The aortic dissection is a medical condition that is associated with severe pain caused by the aorta tearing into layers and that causes circulatory disturbance at a bifurcation. In the aortic dissection, a tear (an entry) appears in an intima, and as blood flows into the entry, the intima is separated, which leads to a double-lumen structure of a true lumen and a false lumen. The aortic dissection has a high mortality rate, and approximately 93% of the cases leads to death within 24 hours of onset.
A diagnosis of the aortic dissection can be made by using contrast imaging CT (computed tomography), MRI (magnetic resonance imaging), and ultrasound. Generally, the contrast imaging CT is used prior to an operation, and transesophageal echocardiography is used during an operation.
The aortic dissection is typically treated by removing the aorta including the torn region that has appeared in the intima and replacing with an artificial blood vessel. However, in the aortic dissection, the aorta may rapture while redoing CT imaging, and thus an operation is sometimes started without obtaining sufficient information for the pressing urgency.
In a case of a patient with a wide area of a flap (an intimal flap) that moves in accordance with pulsation, the entire flap may not be replaced with an artificial blood vessel depending on a physical strength of the patient. If that is the case, it is typical that only a region that is close to an aortic valve is replaced with an artificial blood vessel and the remaining region is treated through pharmacotherapy or the like. In such a case, even if a sufficient amount of blood is fed during the operation, the flap may block part of bifurcated arteries, which may lead to circulatory disturbance in organs beyond the blocked bifurcated arteries. In addition, a site of a flap may change, and thus, during the operation, it is necessary to proceed with the treatment while checking on the blood circulation in the aorta and the organs based on images from transesophageal echocardiography (TEE).
With an existing technique, there is a risk of overlooking a bifurcated artery that can be blocked by a flap during an operation for the aortic dissection using the transesophageal echocardiography. Furthermore, with an existing technique, there is a risk of overlooking circulatory disturbance that occurs at an unexpected location due to a flap moving within a range of a dissected intima during an operation for the aortic dissection using transesophageal echocardiography.
That is, with the existing techniques, a flap cannot be confirmed with high precision during an operation for the aortic dissection using transesophageal echocardiography.